1. Field of Invention
This invention relates to a pressure sensor which detects changes in pressure as displacement or torque in a movable plate; and more particularly, to a pressure sensor capable of effecting measurement of delicate changes in pressure, for example as small as that of a 0.01 .mu.m water column. The invention can be used to detect infrared rays which can cause pressure changes in a chamber through which the rays are directed.
2. Description of the Prior Art
Condenser microphones are well known as pressure sensors which are capable of measuring small pressures. The condenser microphone generally comprises a metal film which receives the pressure and a fixed electrode which is disposed opposite the metal film. It detects the displacement of the metal film caused by the pressure, such displacement being defined as a change in electrostatic capacities between the metal film and the fixed electrode.
However, the prior devices have a disadvantage in that they are impossible of attaining favorable characteristics because of the non-uniformity of the sensitivity of detection, and in that to attain some measure of uniformity, the metal film is stretched so as to apply tension to the entire surface which causes other problems. Moreover, the sensitivity of detection is high under those conditions, but, on the other hand, such prior devices tend to be then influenced by vibration noises and by changes in position or posture. Other deficiencies are known to exist and hence these prior device leave much to be improved upon.